Not sure if this is the right forum for this topic. Please move this if needed

This is rather a general technology question. I live in an apartment, and we have a buzzer that connect to each unit, it operates on the telephone line. So when you dial a buzzer number, the unit's telephone rings, and you hold onto 0 or some other number and the door will open down stairs.

My goal is to have a Raspberry Pi connected to a 56k USB modem and connected to the telephone jack.

I am trying to achieve the following:

- User dials the buzzer code
- The Raspberry Pi picks up the telephone (with the use of the modem)
- User enters a "secret code" eg) 1234
- Raspberry Pi decodes the "secret code"
- If the code matches, the Raspberry Pi presses and holds the open door button for 5 seconds.

I basically need for the RPi to be able to answer the phone, decode analogue signals to pick apart the numbers and reply by pressing buttons. I've been looking at PBX systems, and am wondering if there are any specific pointers out there for projects like this.

Not sure if this is the right forum for this topic. Please move this if needed

This is rather a general technology question. I live in an apartment, and we have a buzzer that connect to each unit, it operates on the telephone line. So when you dial a buzzer number, the unit's telephone rings, and you hold onto 0 or some other number and the door will open down stairs.

My goal is to have a Raspberry Pi connected to a 56k USB modem and connected to the telephone jack.

I am trying to achieve the following:

- User dials the buzzer code
- The Raspberry Pi picks up the telephone (with the use of the modem)
- User enters a "secret code" eg) 1234
- Raspberry Pi decodes the "secret code"
- If the code matches, the Raspberry Pi presses and holds the open door button for 5 seconds.

I basically need for the RPi to be able to answer the phone, decode analogue signals to pick apart the numbers and reply by pressing buttons. I've been looking at PBX systems, and am wondering if there are any specific pointers out there for projects like this.

OR

what if the pi could be accessed by another means like a mobile phone, and then was connected across the door release button?

I vaguely remember causing all sorts of trouble on campus phone lines using a modem, Win NT and "hyperterminal"... Perhaps something like that could do what you need.
I think Linux equivalents are gkterm or minicom

With an appropriate USB to RS232 adapter and a (non-winmodem) 56K modem you should be good to go.

The biggest problem is that most 56K modems are Winmodems (which relied on some of the code running on the windows side of the interface). You'd get 300/300 or 1200/75 modems running easily. Even with the Linmodem project you're going to struggle.

I think that technologically your plan is going to have its biggest hurdle on "decode analoge signales" part.
I've used a fair share of modems in the 80's and 90's but can't remember any that did DTMF decoding, most of them didn't have any analog audio output, and the Pi doesn't have an audio input.

Firstly, are you sure that the circuit from the door to the apartment is actually a telephone line, and not a closed circuit with a doorphone. A doorphone may look like a phone, but may only actuate relays on pressing a specific button, and therefore run at different electrical specification.

If it is a phone circuit, then you can use a USB modem, along with asterisk (or one of the many pbx distributions) and one of any number of scripts. Further info can be found at voip-info

It might be worth actually finding out what the door interface is, as there may be other options.

This is a device that connects to the phone and then to an ethernet work. This can convert the analog phone line signal to a SIP signal.

Then forward the SIP connecting to the RBI, there install Asterisk (http://www.asterisk.org/) you can then program a dial plan to do whatever you want with the DTMF tones.

BTW Once you have your phone line connected with the FXS and into Asterisk running in the RBP you can do all sort of things with it. Like have it call you for notifications and allow tones commands or a full phone menu that can do all sort of things.

Not sure if this is the right forum for this topic. Please move this if needed

This is rather a general technology question. I live in an apartment, and we have a buzzer that connect to each unit, it operates on the telephone line. So when you dial a buzzer number, the unit's telephone rings, and you hold onto 0 or some other number and the door will open down stairs.

My goal is to have a Raspberry Pi connected to a 56k USB modem and connected to the telephone jack.

I am trying to achieve the following:

- User dials the buzzer code
- The Raspberry Pi picks up the telephone (with the use of the modem)
- User enters a "secret code" eg) 1234
- Raspberry Pi decodes the "secret code"
- If the code matches, the Raspberry Pi presses and holds the open door button for 5 seconds.

I basically need for the RPi to be able to answer the phone, decode analogue signals to pick apart the numbers and reply by pressing buttons. I've been looking at PBX systems, and am wondering if there are any specific pointers out there for projects like this.

You State it works on the phone line but are you sure it is not a Standalone Phone Entry System if so does it have amanufacturers name

I have the exact same issue.
The door system is phone line based, visitor dial app. number at the door, it rings my phone line. I answer then press a specific button (ex: number zero) to unlock the door.
I would like my Raspberry to answer the phone via USB 56k modem, listen for a specific DTMF, then send DTMF to unlock the door.

Has anyone found an answer for that?
I know these posts are from 2015 but it still an issue for me.

I would like my Raspberry to answer the phone via USB 56k modem, listen for a specific DTMF, then send DTMF to unlock the door.

If it were a standard serial port modem it would be easy. Just send the right AT commands to have it report the ring and decoded DTMF tones. All you need to do then is wait for the the ring, pick up the line, wait for the DTMF reports, check those, activate the door release or don't, hang-up and repeat.

If you can find a way for the Pi to see the modem as a serial interface through which to send AT commands it should be the same.

You definitely don't have to use a modem, but it does make things easier. You need a modem with "voice" capability. This allows you to capture sound from the phone line, and play sound out to the phone line. The advantage of using a modem is that modems are designed to be able to monitor the line for calls and answer them. The modem does not need to be 56k - any modem which has "voice" capability will do. You can do the DTMF coding / encoding in software on the Pi itself.

All (hayes compatible) external modems with a serial connector are modems that have a built in signal-processor, mostly with a Rockwell chip or something similar.

Winmodems are crap, and use most of the CPU power just to do the audio processing, its just that they were cheap and customers didn't know better, they were barely good enough to access bulletin board systems.